Printing apparatuses which print information such as a desired character or image on a sheet-like printing medium such as a paper sheet or film are widely used as an information output apparatus in a word processor, personal computer, facsimile apparatus, and the like. These printing apparatuses are used as printers in current business offices, in other business affairs departments, and for personal use. The printing apparatuses have been developed and improved for achieving further cost reduction, higher resolution, and the like while strongly requiring high density and high-speed printing.
Of these printing apparatuses, an ink-jet printing apparatus which discharges ink from the orifices of printing elements to perform printing as quiet nonimpact printing can realize high density and high-speed printing because of its structural feature, and is widely spread as a low-cost color printer or the like. The ink-jet printing apparatus performs printing by discharging ink in accordance with desired printing information by using a printhead having a printing element (nozzle) with an orifice and an electrothermal transducer which generates discharge energy for discharging ink from the orifice.
As the printhead structure, various printheads in which a plurality of printing elements are aligned in one or a plurality of lines have conventionally been known. In a printhead of this type, N printing elements are designed as one block, and several or several dozen driving integrated circuits which can be simultaneously driven are mounted on a single board. Image data are aligned in correspondence with printing elements, and arbitrary printing is done on a target printing member (printing medium) such as a paper sheet.
With recent increases in resolution and image quality, the printhead performance has greatly been improved. The number of printing elements to be simultaneously driven increases because the number of printing elements has been increased or in order to increase the printing speed.
As the number of printing elements to be simultaneously driven becomes larger, energy necessary for driving also becomes larger. A printing element driving method corresponding to the capacitance of a power supply circuit is required. For a printing element which performs printing by using heat, continuous driving of one printing element accumulates heat, changing the printing concentration or destructing the printing element itself. In the presence of a factor such as manufacturing variations, proper printing element energy cannot be obtained for application energy, which degrades the printhead durability or the like.
A printing element is also influenced by an adjacent printing element. For example, in an ink-jet printing apparatus, when adjacent printing elements are simultaneously driven, nozzles receive pressure interference owing to a pressure generated in ink discharge. The pressure interference (crosstalk) may change the printing concentration. It is, therefore, desirable to set an idle time for dissipating heat or avoiding crosstalk.
To cope with these problems and demands, there is proposed an arrangement in which the printhead incorporates, e.g., a means for detecting a printhead temperature, a means capable of arbitrarily changing a driving method by an external input signal, and a means for detecting the difference between printheads due to manufacturing variations, and if necessary, pieces of information are extracted and controlled.
Various types of printheads are proposed in accordance with the performance of the printer main body, and a printhead having information for identifying the type of printhead is also available. In particular, an ink-jet printhead has various pieces of printhead information necessary for the printer main body, such as the ink use amount of an expendable ink cartridge.
A circuit arrangement in which printing elements are grouped into a plurality of blocks every predetermined number of printing elements and the blocks are driven in time division is put into practical use.
In a printing apparatus using such printhead, the number of printing elements in the printhead increases, and the density also tends to increase for the purpose of high printing speed and high printing density. Accordingly, the number of blocks in the above-mentioned time division driving increases, and the number of control signal lines also increases even in the use of a decoder circuit or the like. As the image quality and function are improved, the printhead structure becomes complicated, and its control becomes cumbersome, overloading the control unit of the main body apparatus. For example, the control unit must manage/execute a control sequence of, e.g., changing a driving pattern in accordance with the printing mode such as high-image-quality printing or high-speed printing, manage and calibrate the influence of the difference in printing state on an image owing to printhead manufacturing variations or the difference between lots, determine the type of head, or sequentially monitor the driving status.
As for collecting information for determination of the type of head or the like, a recent printhead has a data holding function such as a nonvolatile memory (to be simply referred to as a memory hereinafter). The memory stores, as printhead feature information, data such as manufacturing variation information of a printing element or temperature sensor, manufacturing time information containing a printhead manufacturing date, printhead structure information, and a printhead printing dot count value. The printhead memory holds data such as the feature information in a non-rewritable or rewritable state. When, for example, the printhead is mounted on the main body apparatus, all stored data are read out. Necessary information is reflected in the internal register of the main body apparatus or the like, realizing control corresponding to each printhead. The main body apparatus refers to mapping information which makes the type of information and a storage position correspond to each other, extracts information necessary for control from all data read out from the printhead memory, and utilizes the information for various control operations.
In real-time driving control of performing driving coping with, e.g., temperature detection during printing, processing in correspondence with mapping during read of data (feature information or the like) from the memory decreases the throughput, failing to achieve high-speed, high-image-quality printing. Especially for a thermal head and thermal ink-jet head, the printing temperature greatly influences a printed image. Hence, driving energy control corresponding to the printhead temperature is important, and is an indispensable function for a high-image-quality printing apparatus. The main body apparatus must send a large amount of printing data to the printhead at a high speed, and it is difficult to execute control during detection of head information in terms of the processing time.
The control load on the apparatus main body is heavy in a conventional arrangement in which the apparatus main body performs fine driving control not only for read of head information but also for, e.g., adjustment of a driving signal for driving the printing element of the printhead.
One problem of the prior art is that fine control processing for performing predetermined head processing is executed by the control circuit of the apparatus main body.
Further, read of data from the printhead takes a long time because all data in the head are conventionally read out to the apparatus and necessary data are selected and used in the main body apparatus in acquiring head information. This can be ignored when data is read out from the printhead at a timing when a sufficient time can be used for read (e.g., a timing when the apparatus is powered on). However, when data must be extracted from the printhead within a short time for real-time driving control such as the above-mentioned temperature detection and driving signal control, no time can be ensured for information acquisition and control processing.
Every time the number of types of printheads increases, mapping information of the memory for each printhead must also be set, and read processing in the main body apparatus must be changed for each type of printhead. To allow the main body apparatus to extract common specific information from various types of printheads by the same read processing, the memory storage method and storage address must be common between different types of printheads. In this case, the degree of freedom of using a memory for each head is greatly limited.
The above-described technical background requires a printhead to perform predetermined processing by a simple control instruction to a carriage or head without outputting a fine control signal from the control circuit of the apparatus main body (circuit board of the apparatus main body) to the head when the printhead performs predetermined processing.
It is also required to efficiently extract information held by the printhead.
It is further required to acquire necessary information from the printhead at a high speed.
It is still further required to increase the degree of freedom of using a memory mounted in the printhead.